<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>10.outerHTML</title>
  </head>
  <body>
    <div id="demo">
      <h2>你好</h2>
      <h3>Hello</h3>
    </div>
    <script type="text/javascript" >
      let demo = document.getElementById('demo')
      console.log(demo.innerHTML)
      console.log(demo.outerHTML)
    </script>
  </body>
</html>